Trial and error is useful but frustrating

My diamond grinding book arrived and I bought 360 and 600 grit diamond paste and two uncharged disks. The diamond worked as advertised. I sanded eleven stones before I had to recharge the disk. After eighteen stones it does not look worn. I'm well pleased about that.

However, I'm less than pleased with three errors I made:

1. I tried to do a huge batch at a time
2. I insisted on trying to work little stones in my fingers instead of dopping them
3. I experimented with my polishing

Re: #1 -- I decided to gather all of the found rocks that we'd collected so far. After cleaning and using the trim saw on the first batch (one more batch of found rocks before I get into the rocks we've found at the mines) I had sixty-four stones ready for the 100 grit wheel. I had been trying a new method that would get my stones closer to being sellable. After grinding forty-eight on the 100 grit I figured out how to get closer to that goal and that my current stones had domes that were too narrow and high. That is the first problem with doing large batches. If you try to do things in a repeatable fashion and you make a mistake, all of the items in the given batch will have the same mistake. Correcting the mistake would mean removing a great deal of material. So, even though nothing was lost and I did learn how to improve my method, it is incredibly frustrating to have 48 stones with the same error. The second problem with large batches is focus. After 1-4 hours of repetitive work I tend to go cross-eyed. Ridges and bumps that show up during 100 and 220 grit grinding are often small. But they stand out clearly after prepolish. The more I did, the more I missed.

Very frustrating.

Re: #2 -- Dopping stones is a bit of work... especially a large number of stones. Normally, it is easier to grind while holding the stone in my fingers. But once the stone gets to be under a centimeter, it is very difficult. Plus I manged to grind away around a third of the fingernails on my index and middle fingers of both hands. In the end my smaller stones had many ridges.

Re: #3 -- I had read that faceters sometimes mixed their diamond grit in petroleum jelly instead of oil. I had been mixing my polish in water and painting it onto the felt pad. As that was a bit messy I thought mixing it with petroleum jelly might be better. It wasn't. Best as I can tell, once the water drys up on a given polishing run the polish acts like it is bonded with the felt. This makes the polishing action much more aggressive. When the polish is mixed with petroleum jelly it never gets aggressive and the stone never gets a proper shine.

So, I now have eighteen stones with a crummy polish and thirty more with the error mentioned above.

grr

Might as well write down my current method (which is nothing more than a hodgepodge of what I've read).

1. Trim saw
2. Rough forming
3. Fine forming
4. Sanding/smoothing
5. Polishing

#1 -- Use the trim saw to get around 1.5-2mm of the drawn outline.
#2 -- Dop small stones! While holding the stone so that its bottom is on top, grind to around half a millimeter of the outline then flatten the bottom. Then grind the edge flat (about a 1/4mm from the outline). Measure and mark off the top of the bezel, which should be one third the height of the stone. "Mark the top of the stone in thirds from end to end and side to side"*. Then make a dot in the center of that marking. While continuing to hold the stone with the bottom on top, grind to around a quarter millimeter of both the bezel line and the line drawn on the top of the stone. Once the entire top of the stone has been ground that way, grind to the dot at a lesser angle. Lastly remove any large ridges or facets before rinsing off the stone.
#3 -- Lightly grind all over the sides and top of the stone to improve later polishing. Remove all ridges, facets, and bumps because sanding/smoothing will not remove them. If there are any major errors found at this stage (like an asymmetrical shape), go back to the 100 grit.
#4 -- Being careful to avoid the bezel line, sand all over the stone to improve later polishing. It is at this point ridges that were missed during steps 2-3 will begin to stand out. If you find them, go back to the 220 wheel.
#5 -- Same procedure for both tripoli and cerium oxide: mix polish with water and dab onto pre-moistened felt pad. Starting on the outside while the pad and polish are wet, use moderate pressure and twist and rock the stone. As the pad drys move towards the center of the pad. When you feel the pad tugging at the stone pay attention to heat and stay near the center of the pad. Do this all over the stone for a dull shine with the tripoli and a good luster with the cerium oxide. Note: if you are too near the outer edge of the pad when it starts to dry, you will get pitting and an odd "flow" of stone in the area worked. The only way to get rid of that is to go back to the sanding step.


At this point I'm going to try batches of five stones and finish off the eighteen stones that have been rough formed. Then I can test out grinding to both bezel and top markings.


* Cabochon Cutting by Jack Cox